Grinding machine

ABSTRACT

This invention relates to a grinding machine having means for assuring that the spindle deflection is the same during the critical portions of successive grinding cycles, irrespective of variations in workpiece size.

United States Patent Uhtenwoldt 14 1 Sept. 19, 1972 [54] GRINDING MACHINE [56] References Cited [72] Inventor: Herbert R. Uhtenwoldt, Worcester, UNITED STATES PATENTS Mass 3,417,512 12/1968 Robillard et a] ..5l/165.9l I731 Awgnw The Bald Machine Company, 3,503,158 3/1970 Robillard et a1. ..5l/l65.8

3,534,509 10/1970 11mm et al. ..5l/165.91

[22] Flled: July 1970 Primary Examiner-Harold D. Whitehead Appl- NO-I 53,491 Attomey-Norman S. Blodgett 52 us. 01. "51/1 5592, 5l/l65.8 [57] ABSTRACT [51] Ill. (:1. ..B24b 49/16 Th s invention relates to a grinding machine having Field of means for assuring that the Spindle deflection is [he same during the critical portions of successive grinding cycles, irrespective of variations in workpiece size.

STEPPI& MOTOR 6 Claims, 3 Drawing Figures HAND WHEEL FOR ---1 posmomue 155555161 carpzamu SL'DE AND SWITCH ung LAM-ALLY l m FEED STOP BALL SCREW 32 v 34 ED SWITCH 2 21111111111 f 31 LLJJ-u/ 35 "1:; 7T

as 2a 35 J E CONTROL T E -1 1 I l I mess L 1' F Lil 33" SLIDE :1:

4 WHEELHEAD 1a 2 22 27 1 1 26 'LMBFL 1 '5 1955715 s O'CLOCK SH E |g1 I 1 11 I I l l I l I I '1 I 1 TABLE I 1 I I 1 l .12 l 1 1 I 1 '1 =5 NOTE WORKPIECE,TOOLING.AND DIAMOND RECIPROCATE DURING GRIND.

PATENTED sir I 9 I972 STEPPI& MOTOR SHEET 1 0F 3 III VALVE CONTROL B OX IHAND WHEEL IFOR POISITIONING SLIDE DRESS STOP COMPENSATION AND SWITCH SLIDE MNUALLY FEED STOP ,MD SWITCH H SIZE CONTROL CROSS SLIDE 22 I I WHEELHEAD 27 2s DIAMOND l6 WORKPIECE t 3 O'CLOCK SHOE l5 i I? l8 I I f I I as y I I I22: -v l I I I I g TABLE I I I -E I I 1 I I I l I I l i F|G.|

I 39 I l l l NOTE= WORKPIECE,TOOLING,AND DIAMOND RECIPROCATE DURING GRIND.

INVENTOR.

HERBERT R. UHTENWOLDT ATTORNEY mcmrznm 19 m2 DISPLACEMENT sum 2 or 3 POSITION CONTROLLE FORCE WHEEL POSITION flflifl. CONTACTS WORKPIECE ROUGH GRIND RETRACTION (SYSTEM FINAL sIZE TATE STOP FEED GAGE FEED RATE Q 1 ,NORMAL Q L E Z9 EARLY GAGE WHEEL CONTACTS WORKPIECE WHEN SLIDE CONTACTS STOP \LAG 0F WHEEL IN RESPECT TO DEF'LECTION) DRESS FINISH GRIND SLIDE TIME GRINDING MACHINE BACKGROUND OF THE INVENTION When one attempts in internal grinding to obtain consistent size, finish, and shape in the workpieces, a considerable problem is encountered. If the rough workpieces have variations, this causes the grinding wheel to enter into the finish portion of its cycles with various amounts of deflection in the spindle. Attempts in the past to overcome this deficiency of internal grinding machines have met with little success and, as a result, there has been a tendency to perform the rough grinding portion of a grinding cycle at a lower force than is possible if the breakdown of the wheel were the only limitation. This results in longer work cycles and, therefore, an inefiicient use of the capital investment represented by the machine. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a grinding machine wherein the deflection in the spindle is the same from workpiece to workpiece, despite variations in the initial characters of the workpieces.

Another object of this invention is the provision of a grinding machine in which maximum force during rough grinding can take place without introducing undesirable differences in the deflections of the spindle as finish grinding takes place.

A further object of the present invention is the provision of a grinding machine having a variable wheel slide retraction to obtain a constant spindle spring prior to sparkout or final grind.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

SUMMARY OF THE INVENTION In general, the invention has to do with. a grinding machine having a base on which are mounted a wheelhead and a workhead, a hydraulic feed cylinder being provided to bring about relative feeding motion between them. When the workpiece bore size reaches an intermediate point, the pressure to the feed cylinder is reduced to zero (or a predetermined, constant low pressure). The spindle deflection forces the wheelhead slide in the direction opposite the feeding direction until the deflection has been relieved. A slide stop is rapidly advanced until contact is made with a compensation slide and feed is then continued at a predetermined feed rate.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a plan view, with portions broken away, of a grinding machine embodying the principles of the present invention,

FIG. 2 is a diagrammatic view of a grinding cycle incorporating the principles of the present invention, and

FIG. 3 is a somewhat more detailed cycle diagram of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, wherein are best shown the general features of the invention, the grinding machine, indicated generally by the reference numeral 10, is shown as being of the type shown and described in the patent application of Edward G. Robillard et al., Ser. No. 879,785 filed Nov. 25, 1969 and now US. Pat. No. 3,634,979. It is provided with a base 11 on which is mounted a workhead table 12 and a wheelhead cross slide 13. Mounted on the workhead table 12 is a workhead 14 rotatably carrying a workpiece 15 having a bore 16 whose surface is to be finished. The workpiece 15 is mounted with its outer periphery carried on fixed shoes 17 and driven by a magnetic platen 18. The table l2 is mounted on ways 19 and 21 for movement longitudinally, or in the direction of the axis of the bore 16. A dressing apparatus 22 is mounted on the table adjacent the workpiece.

The cross slide 13 is mounted on ways 23 and 24 for movement transversely of the axis of the bore. The way 24 includes a hydraulic cylinder for bringing about such lateral movement. Mounted on the cross slide 13 is a wheelhead 25 in which is rotatably carried a spindle 26 whose outer end carries an abrasive wheel 27. Between the ways 23 and 24 under the cross slide 13 and resting on the upper surface of the base 11 is a compensation slide 28 which is movable transversely by means of a first stepping motor 29 operating through a screw 31. Extending downwardly from the cross slide 13 is a horn 32 which lies in a notch 33 formed in the compensation slide. Mounted at the front of the cross slide is a retractable stop 34 which is cooperative on occasion with a hardened metal pad 35 formed on a forwardly directed surface of the compensation slide 28. The stop 34 is movable relative to the cross slide by means of threads 36 and can be rotated by a second stepping motor 37 mounted on the cross slide. A gage 38 extends through the workhead to indicate when the bore 16 reaches a predetermined size, at which time it is able to enter the bore and operate a switch 39.

The operation of the invention will now be readily understood in view of the above description. In FIG. 2,

, it can be seen that the graph A represents the position of the wheelhead cross slide 13 during the grinding cycle, while the line labeled B shows the wheel position. The hydraulic cylinder incorporated in the way 24 moves both the wheelhead 25 and the wheel 27 transversely from the point a to the point b. At this last point, the wheel 27 contacts the surface of the bore 16 and grinding begins. The hydraulic fluid supplied to the way-cylinder 24 causes a grinding force to build up between the abrasive wheel and the workpiece, so that the spindle 26 is bent (or other component elements tooling, workpiece, table are deflected) and the wheel position B and the slide position A begin to deviate. Grinding takes place under the controlledforce principle until the gage 38 indicates that the bore 16 has reached a dress size; in other words, the end of the rough grind indicated on the chart by the point C At that time, the slide has reached a point C,, the difference being represented by the deflection in the system. As soon as the gage 38 enters the bore, the switch 39 is operated, and this serves to reduce the pressure fluid in the cylinder 24 to zero. With the buildup of deflection in the spindle, the forces thus cause the slide 13 to move to the front of the machine, increasing the gap between the stop 34 and the pad 35 on the compensating slide 28. As soon as sufficient time has passed for the spindle to lose its deflection, the main controls in the machine operate the second stepping motor 37 to cause the shaft to rotate and the stop 34 to advance toward the pad 35. When contact is made with the pad 35, it acts as a switch in an electrical circuit, and pressure fluid is reintroduced into the feed cylinder in the way 24. This fluid causes the cross slide 13 to be pressed rearwardly, so that the stop 34 presses tightly against the pad 35. Then, the main control serves to operate the second stepping motor 37 in the reverse direction, thus backing the stop 34 away toward the front of the machine and causing the cross slide to move rearwardly.

The abrasive wheel 27 advance into the surface of the bore 16 from the point d, through the point e on a pre-determined feed rate determined by the number of pulses introduced into the stepping motor 37. The feed is stopped at the point e and the wheel operates on sparkout to the final point f.

The process (without interruption for dressing between roughing and finishing) is shown in somewhat more detail in FIG. 3 where the graph represents the movementof the wheel relative to the workpiece surface. The wheel advances at a low value of controlledforce from the point a to the point b where the force in the cylinder is increased appreciably for rounding up and stock removal. This operation takes place to the point e where a size contact on the slide indicates that this point is reached and the gage is energized and placed in condition for measuring the bore size. Rough rate is continued to the point d where the stop 34 engages the pad 35 on the compensation slide. According to this method of operating the machine, the main control then. operates the second stepping motor 37 to cause the stop 34 to move forwardly and thus allow the slide to move rearwardly and cause grinding to take place at a predetermined rate from the point d to the point e. At that point, the pressure on the cylinder is relieved and the spindle deflection causes the slide to move forwardly and reduce the spindle deflection appreciably to the point f. Grinding takes place at a predetermined spindle deflection for sparkout to the point 3, at which time the wheel is backed off to the point It and a dressing cycle may take place. Dressing may be skipped, if so desired. Compensation then takes place, loading takes place, and work is begun on a new workpiece.

lt can be seen that, by operating the apparatus in the manner described, it is possible to obtain the finish grinding of a workpiece, whether it be at a low value of feed rate or by sparkout, by starting that finish portion of the cycle with a zero (or very low) value of spindle deflection. This same spindle deflection is present, ir-

respective of the initial shape, size, or finish of theworkpiece surface, so that it will accomplish consistent size, shape, and finish of the finished surface in a succession of workpieces.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly cone within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent lclaim: l. A grinding machine, comprising: a. a base on which are mounted a workhead and a wheelhead,

b. feed means for bringing about relative movement between the workhead and the wheelhead in a first direction to cause grinding engagement with a predetermined force between a workpiece mounted on the workhead and an abrasive wheel mounted on the wheelhead,

c. means operative at the end of a roughing grind to substantially reduce the force produced by the feed means, so that relative movement between the workhead and the wheelhead takes place in av direction opposite to the said first direction,

because of deflection forces stored in the wheelhead,

a feed stop mounted on the wheelhead and movable relative thereto,

e. a compensation stop mounted on the base,

f. a motor operative at the end of the relative movement between the workhead and the wheelhead in the said opposite direction to move the feed stop until it engages the compensation stop, and

' g. means operative when the feed stop engages the compensation stop to increase the force produced by the feed means to a higher value and to cause the motor to move the feed stop to bring about grinding at a predetermined rate.

2. A grinding machine for finishing a surface of revolution of a workpiece, the surface being concentric to a major axis, comprising:

a. a base,

b. a workhead table element mounted on the base and adapted to support the workpiece,

c. a wheelhead cross-slide table element mounted on the base and adapted to support a rotatable spindle with an abrasive wheel,

d. means for supporting one of the elements for sliding motion transversely of the major axis of the surface revolution,

e. a fluid motor connecting the base to the said one of the elements to bring about the said sliding motion,

f. a secondary slide associated with the said one of the elements and mounted for sliding transverse motion independently of the said one of the ele-. ments,

. a first stepping motor connecting the base to the secondary slide for bringing about its sliding motion,

. a retractable stop mounted on the said one of the elements and engageable on occasion with the secondary slide,

. a second stepping motor connected to the stop, which in turn engages the secondary slide to produce the sliding motion of the said one of the elements, and

' j. control means to cut off fluid pressure to the fluid motor, to allow deflection in the spindle to move abrasive wheel mounted at the free end, and wherein a dressing apparatus is mounted so as to be free of the movement of the said one of the elements and of the secondary slide.

4. A grinding machine as recited in claim 3, wherein the said one of the elements is the wheelhead crossslide table element, wherein the workhead table element is mounted for longitudinal movement relative to the wheelhead cross-slide table element, and wherein the secondary slide is a compensation slide.

5. A grinding machine as recited in claim 4, wherein a control is provided to actuate the stepping motors so that the first stepping motor is used for dress compensation movements and the second stepping motor is used for a feed rate grinding movement.

6. A grinding machine as recited in claim 5, wherein the fluid motor is a hydraulic cylinder connecting the wheelhead table element to the base to produce a controlled-force grinding movement. 

1. A grinding machine, comprising: a. a base on which are mounted a workhead and a wheelhead, b. feed means for bringing about relative movement between the workhead and the wheelhead in a first direction to cause grinding engagement with a predetermined force between a workpiece mounted on the workhead and an abrasive wheel mounted on the wheelhead, c. means operative at the end of a roughing grind to substantially reduce the force produced by the feed means, so that relative movement between the workhead and the wheelhead takes place in a direction opposite to the said first direction, because of deflection forces stored in the wheelhead, d. a feed stop mounted on the wheelhead and movable relative thereto, e. a compensation stop mounted on the base, f. a motor operative at the end of the relative movement between the workhead and the wheelhead in the said opposite direction to move the feed stop until it engages the compensation stop, and g. means operative when the feed stop engages the compensation stop to increase the force produCed by the feed means to a higher value and to cause the motor to move the feed stop to bring about grinding at a predetermined rate.
 2. A grinding machine for finishing a surface of revolution of a workpiece, the surface being concentric to a major axis, comprising: a. a base, b. a workhead table element mounted on the base and adapted to support the workpiece, c. a wheelhead cross-slide table element mounted on the base and adapted to support a rotatable spindle with an abrasive wheel, d. means for supporting one of the elements for sliding motion transversely of the major axis of the surface revolution, e. a fluid motor connecting the base to the said one of the elements to bring about the said sliding motion, f. a secondary slide associated with the said one of the elements and mounted for sliding transverse motion independently of the said one of the elements, g. a first stepping motor connecting the base to the secondary slide for bringing about its sliding motion, h. a retractable stop mounted on the said one of the elements and engageable on occasion with the secondary slide, i. a second stepping motor connected to the stop, which in turn engages the secondary slide to produce the sliding motion of the said one of the elements, and j. control means to cut off fluid pressure to the fluid motor, to allow deflection in the spindle to move the said one of the elements until the deflection is relieved, to cause the second stepping motor to advance the retractable stop until it engages the secondary slide and, when the stop engages the slide, to retract the stop at a predetermined rate.
 3. A grinding machine as recited in claim 2, wherein the surface of revolution which is to be finished is an internal surface, wherein the spindle is mounted with one end carried in a bearing and the other end free with the abrasive wheel mounted at the free end, and wherein a dressing apparatus is mounted so as to be free of the movement of the said one of the elements and of the secondary slide.
 4. A grinding machine as recited in claim 3, wherein the said one of the elements is the wheelhead cross-slide table element, wherein the workhead table element is mounted for longitudinal movement relative to the wheelhead cross-slide table element, and wherein the secondary slide is a compensation slide.
 5. A grinding machine as recited in claim 4, wherein a control is provided to actuate the stepping motors so that the first stepping motor is used for dress compensation movements and the second stepping motor is used for a feed rate grinding movement.
 6. A grinding machine as recited in claim 5, wherein the fluid motor is a hydraulic cylinder connecting the wheelhead table element to the base to produce a controlled-force grinding movement. 